Apparatus and method for checking the diameter of elongated structures

ABSTRACT

Apparatus and method for checking the diameter of elongated structures, such as cables and insulated conductors, without contact and destruction, in a continuous manner, by passing the structure axially through an ionization device, providing radioactive radiation which impinges on the structure while it passes through the chamber, allowing the radiation to be weakened by its passage through the structure and to act upon electrode means also disposed in the chamber, and measuring the ionization current generated by the electrode means, the current being representative of the diameter of the structure as it passes through the device.

United States Patent [72] Inventors [54] APPARATUS AND METHOD FORCHECKING THE DIAMETER OF ELONGATED STRUCTURES [56] References CitedUNITED STATES PATENTS 2,875,364 2/1959 Herzog 313/93 2,899,582 8/1959Hermsen et a1 313/93 2,922,884 1/1960 Fearnside 250/83.3 D X 2,964,63012/1960 Bosch 250/83.3 D X 2,965,758 12/1960 Malick 250/106 S 3,449,5756/1969 Smith 250/106 S Primary Examiner-Archie R. Borchelt Attorney-TabT. Thein ABSTRACT: Apparatus and method for checking the diameter ofelongated structures, such as cables and insulated conductors, withoutcontact and destruction, in a continuous manner, by passing thestructure axially through an ionization device, providing radioactiveradiation which impinges on the structure while it passes through thechamber, allowing the radiation to be weakened by its passage throughthe structure and to act upon electrode means also disposed in thechamber, and measuring the ionization current generated by the electrodemeans, the current being representative of the diameter of the structureas it passes through the device.

PATENTEU SE P28 1911 SHEET 1 OF 2 FIG. 2

IIII.

NVENTOR J'URGEN KNORR eial BY a1 AGENT PATENTED SEP28 l9?! SHEET 2 BF 2CURRENT INDICATOR SOURCE PRODUCTION EQUIPMENT RE GULATOR INVENTORJ'URGEN KNORR e1 ol AGENT APPARATUS AND METHOD FOR CHECKING THE DIAMETERF ELONGATED STRUCTURES The invention relates to an apparatus and amethod for the continuous, contactless and destruction-free checking orinspection of the diameter of elongated structures, such as eables,insulated conductors and the like. However, both the ap paratus and themethod are adapted for measuring or checking the outside diameter oftubes and other profiles, the type of material being immaterial.

It is known to measure the thickness of elongated structures, inparticular of insulating sheaths of insulated conductors, by mechanicalscanning by means of rollers. The result of the measurement is indicatedon suitable instruments.

In another known method an X-ray tube, focused by means of a mask, isused as a source of rays. The elongated structure to be measured ispassed between the ray source and a luminescent screen so that thestructure is shown directly on said screen. To measure hose-shapedplastic structures in a contactless manner, it is further known todispose an ionization chamber in the interior of the hose, and one ormore emitters on the outside.

In another known method for the contactless measurement of diameters,the elongated structure to be checked or measured is located between aradioactive ray source and a radiation detector. The use of a diaphragmsecures that the elongated structure is hit by an approximately parallelradioactive beam of rays only.

The known methods have a number of disadvantages. The mechanicalscanning method has the disadvantage that the measurement is notcontactless. When thermoplastic materials are involved in the elongatedstructures, particularly in cables and insulated conductors,deformations and injuries to the surfaces may occur. Since themeasurement of the thermoplastic material can normally take place onlyafter its solidification, there are long lapses between the indicationof diameter fluctuations and the initiation of the regulating process.Therefore, for a certain manufacturing period, there is no assurancethat the object or structure tested is actually to size. Beyond this, inchecking the diameter of insulated, stranded conductors, considerabledeviations in the indication of the measured values will occur becauseof the unavoidable stranding twist.

The known optical measuring methods for the inspection of the diameterof elongated structures have not been successful in practicalapplication because the unavoidable dust, oil vapors and the like in themeasuring section alone will lead to an uncontrollable distortion of themeasuring results.

When reproducing the test piece on a luminescent screen by means ofX-rays for purposes of diameter inspection, changes in the position ofthe tested structure may simulate a change in diameter at the measuringsection. Moreover, the employment of X-ray apparatus for such purposesentails much expense in terms of installation and maintenance of thenecessary apparatus.

The use of the method in which an ionization chamber is placed in theinterior of the test piece to be measured, and emitters are disposed onthe outside, is limited to the measurement of the wall thickness ofhose-shaped structures and tubes. The method is not applicable to thecontinuous measurement of the diameter of cables and insulatedconductors.

When using parallel rays of a radioactive source, positional changes ofthe structure under test cause the measured values to change so thatclear information regarding the actual diameter of the elongatedstructure to be measured is not obtainable.

It is the object of the present invention to provide an apparatus and amethod for the continuous, contactless and destruction-free checking andinspection of the diameter of elongated structures, solid or tubular,through which better supervision of the dimensional accuracy of themeasured material or structure is assured while susceptibility totrouble is small.

The invention is based on the task of developing an apparatus and amethod enabling the diameter of elongated structures to be inspected ina contactless and destruction-free manner, independently of thegeometric position of the test piece.

According to important features of the invention, an annular ionizationchamber and a preferably annular radioactive preparation or substancesurround the elongated structure, whereby the intensity of the radiationemitted by the radioactive substance and oriented toward the elongatedstructure is weakened inside the structure, and the radiation intensitypenetrating the sensitive volume of the ionization chamber generates anionization current which represents a measure of the diameter of theelongated structure under measurement, and can be ascertained and evenmeasured in a manner known per se.

The inventive apparatus preferably comprises an annular ionizationdevice having a ray entry window at its inner side facing the elongatedstructure passing therethrough. The radioactive substance is so disposedas to enclose the structure completely.

According to another preferred embodiment of the apparatus, a rotating,punctiform or planar radioactive substance may also be used in place ofthe aforementioned annular substance.

Rotating along with the radioactive substance is, in the modifiedembodiment, a diaphragm or shield whose opening is opposite thesubstrate proper, but the shield otherwise covers up the ray entrywindow.

The apparatus and method according to the invention offer the advantagethat the checking or inspecting installation can be set up in theimmediate vicinity of the forming tools or machines, for instance, inthe immediate vicinity of the nozzle of an extruder for sheathingcables. There is available, without time loss, as the initial value ofthe detection installation, an electrical signal which depends on thediameter of the elongated structure. The signal can be utilized for thecontinuous supervision and control of the manufacturing process.

The consequence thereof is a continuous inspection and regulation of thedimensional accuracy of the elongated structure which is beingmanufactured. Simultaneously with the qualitative improvement of theproduct associated therewith there results the possibility of automaticproduction of elongated structures. By dosing the material batch in, anappropriate manner there result, moreover, savings in material so thatelongated structures of the kind described hereinabove, such as cablesand insulated conductors, among others, can be produced more profitablythan heretofore. It is further possible to pick up several measuringpoints for the diameter control with one central detection installationor instrument.

Another advantage consists in that the apparatus according to theinvention is sturdy, reliable and hardly needs any service ormaintenance.

Other objects, features and many of the attendant advantages of theinvention will be readily appreciated as the same becomes betterunderstood by reference to the following detailed description, whenconsidered with the accompanying drawings, wherein FIG. 1 is a verticalsectional view through a first exemplary embodiment of the inventiveapparatus;

FIG. 2 is a partly sectional view taken along line 22 of FIG. 1;

FIG. 3 is a partial sectional view through a second embodiment of theapparatus;

FIG. 4 is a partly sectional view taken along line 4-4 of FIG. 3;

FIG. 5 is again a partial sectional view, similar to that of FIG. 3,through a third exemplary embodiment;

FIG. 6 is a partly sectional view taken along line 6-6 of FIG. 5; and

FIG. 7 shows a schematic outlay for a testing installation embodying theapparatus and method according to the invention for the automaticregulation of diameters of elongated structures.

Let us refer first to the schematic arrangement shown in FIG. 7,illustrating the method according to the invention for checking thediameter of elongated structures such as, for examples, cables,insulated conductors, tubes, hoses and the like. At 1 such a structureis schematically shown, passing in the direction of the arrow throughand ionization chamber device 2 shown in a somewhat simplified sideelevation. It will be understood that the preferred, exemplaryembodiments of FIGS. 1 and 2, 3 and 4 as well as 5 and 6 illustraterespective devices 12, 32 and 52 which are of course compatible with anusable in the setup of FIG. 7. At 3 and 4, electrical connections areshown for electrodes within the chamber proper, to be described later infull detail. One of the conductors leads to a voltage source 5 while theother goes to a current indicator 6 or the like conventional instrument,preferably in series connection, as shown, with a regulating device 7and control means 8, represented for the sake of simplicity by aconventional motor.

The latter acts on a production equipment 9, such as an extruder and thelike from where the elongated structure 1 is fed toward the ionizationchamber device 2, as shown. The electrical signal obtained at the outputof the indicator 6 is fed to the regulator 7 which, is a known manner,can control the production equipment 9 so that a given nominal size forthe diameter of the elongated structure 1 is maintained during themanufacturing process.

In an exemplary setup, the regulator 7 may consist of a controlamplifier which transforms and amplifies the output value in such amanner that it can be compared with a preset nominal value. Thedeviation between the actually measured and the nominal value can beintroduced into the control means 8 which, in turn, adjusts or regulateseither the payout or discharge speed of the elongated structure 1 or thesupply of plastic compound, or other material, so that a desired nominaldiameter is maintained.

A reversible servomotor may, for example, be used for the control means8, for controlling one of the parameters of the production equipment 9.The latter may represent an extruder, as mentioned before, or a wiredrawing machine, a rolling mill, or the like equipment producingelongated structures of which the inventive apparatus and method checksand monitors the desired constant diameter. Further details of theoutlay of FIG. 7 will not be required since they are not considered toform part of the inventive concept, and are well known to those skilledin various manufacturing arts.

We can now proceed to the description of the first exemplary embodimentas shown in FIGS. 1 and 2. The ionization chamber device is generallydesignated 12, preferably made of two half-shells 10a and 10b (alsoshown in FIG. 7), interconnected by bolts or the like conventionalelements. The device is preferably of annular or disk shape, as shown inFIG. 2. Disk-shaped electrodes 14 are disposed within the shells 10a,10b, in an outer annular space surrounding a ray entry window 16 whichseparates the inner space of the device into a central area for thepassage of the elongated structure 1 and the preferably sealed outerannular area (which could be termed the ionization chamber proper, inwhich the electrodes 14 are secured. The outer annular area ispreferably filled with an ionizable medium. The walls of the device mayconsist of any desired solid material. Preferably an aluminum foil isused for the window 16 between the two chamber spaces or areas.

An annular radioactive preparation or substance 18 is fastened in thisembodiment, by means of an appropriate holder, to the inner side of thewindow 16 which faces the elongated structure 1 during its passagethrough the device 12 (as indicated by the arrow). Holding rings may,for example, be used for fastening the radioactive substance of thisembodiment. It is advantageous for the distance of the substance fromthe lateral planes or walls to be the same; the substance 18 ispreferably centrally disposed within the window 16. The symmetricalarrangement of the apparatus of FIGS. 1 and 2 ensures reliable readingsduring the passage of the structure 1, the radiation intensity beingutilized to the maximum, which is of importance in view of the use ofsmall activities of the substance, and for radiation protection.

It is nevertheless possible to dispose the annular radioactive substance18 laterally in the device 12 or even outside of it (not shown).

At 19, insulator bushings are shown for the aforedescribed electricalconnections 3 and 4 of the electrodes 14. Preferably but not necessarilyinsulating spacers or plates 20 can be provided within the walls 10a,10b for holding the electrodes 14 in their predetermined position.

In the second exemplary embodiment, as shown in FIGS. 3 and 4, someelements are similar to those already described for the previousapparatus embodiment. Thus, numeral 32 denotes the ionization chamberdevice in general; at 30, the walls or half-shells are shown; theelectrodes in the outer annular area are at 34, the window is designated36, and the spacers are shown at 40.

A tubular support member 31 carries a rotatable pulley 46 about which abelt or the like 42 is trained, adapted to be driven from a motor orother drive means. Pulley 46 may be guided about a bearing member 48.This structure serves to carry a rotatable radioactive substance, asshown at 38. The substance is preferably punctiform and is attached tothe free end ofa rod 45 held by the pulley 46. It will be clear from thefigures that the radioactive substance is rotated about the elongatedstructure 1 which passes through the central area of the device 32.

Finally, the third embodiment shown in FIGS. 5 and 6 should be describedwherein some of the structural elements are again similar to thosedescribed before. At 50, the walls of the third ionization chamberdevice 52 are shown; the abovedescribed electrodes and window are at 54and 56, respectively; spacers are illustrated at 60.

As in previous embodiment, a support member 51 is provided for therotation of a pulley 66, driven by a belt 62; numeral 68 again denotesan intermediate bearing member for the pulley. In this embodiment(namely in FIG. 6), a driving shaft 63 is also shown with a pulley aboutwhich the belt 62 is guided for rotation of the radioactive substanceabout the elongated structure.

The substance of this embodiment is preferably planar, as shown at 58,and is attached substantially centrally to a shield or diaphragm 59,rigid with the pulley 66 and extending into the central chamber area, asshown. The opening of the shield is opposite the substance while theshield itself partly covers up the ray entry window 56. IN this manner,the relative changes in the ionization current are increased and, hence,the measuring sensitivity at a given relative change in diameter of theelongated structure 1 as compared to the embodiment without the shieldor diaphragm. The same effect may be obtained with the aforementionedpunctiform substance 38 of the preceding embodiment.

The radiation intensity penetrating from the sensitive volume of theionization chamber device 12, 32 or 52, emanating as it does from theradioactive substance 18, 38 or 58, produces free charge carriers, dueto the ionization action, which carriers are connected on the respectiveelectrodes I4, 34 or 54.

When connecting the voltage source shown in FIG. 7, an ionizationcurrent flows through the system which is sensed by the indicator 6. Dueto the shadow efi'ect of the elongated structure 1 to be measured orchecked, the radiation intensity which penetrates the ionization chamberdevice 2 (or its illustrated practical embodiments 12, 32 and 52) isweakened so that the amplitude of the ionization current represents adirect measure of the diameter of the elongated structure 1.

It is achieved by the symmetry of the arrangement that the ionizationcurrent of the device 2 depends solely on the diameter of the structure1 but not on the specific position of the structure with respect to thedevice, so that changes in position occurring during the manufacturingprocess, or the 4 passage of the structure through the device, remainwithout influence on the measured values.

It should be understood, of course, that the foregoing disclosurerelates only to preferred embodiments of the invention and that it isintended to cover all changes and modifications of the examplesdescribed which do not constitute departures from the spirit and scopeof the invention as set forth in the appended claims.

What We Claim ls:

1. An apparatus for checking the diameter of elongated structures, suchas cables and insulated conductors, comprising, in combination, anionization chamber device having a central area and an outer areaconstituting an ionization chamber, means allowing the movement of anelongated structure through said device in substantially central, axialdirection, a radioactive substance disposed in outwardly spaced-apartrelation to said central area, and electrode means disposed within saidouter area in outwardly spacedapart relation to the structure and saidsubstance, for sensing the radiation which is not absorbed by thestructure, owing to its shadow effect, said electrode means beingadapted to generate an ionization current which is representative of thediameter of the structure as it is moved through said device.

2. The apparatus as defined in claim 1, wherein said outer area of thedevice is annular and said electrode means has an axis of symmetry whichcoincides with that of the structure.

3. The apparatus as defined in claim 1, wherein said radioactivesubstances is disposed closer to the structure than is said electrodemeans.

4. The apparatus as defined in claim 1, further comprising an ionizablemedium in said outer area of the device, for lodging therein saidelectrode means.

5. The apparatus as defined in claim 4, wherein said outer area of thedevice is sealed from said central area, which latter accommodates saidmeans allowing the movement of the structure as well as said substance.

6. The apparatus as defined in claim 5 further comprising window meansbetween said central and said outer areas of the device, said windowmeans limiting said central area in radial direction and allowing theradiation to pass therethrough in its way toward said electrode means.

7. The apparatus as defined in claim 6, wherein said radioactivesubstance is in annular form and surrounds the structure at asubstantially central, stationary location in the proximity of saidwindow means, thereby allowing integration of the entire cross-sectionalarea of the structure by radiation, perpendicular to the longitudinalaxis of the structure.

8. The apparatus as defined in claim 6, further comprising means forrotating said radioactive substance concentrically about the structure,in the proximity of said window means.

9. The apparatus as defined in claim 8, wherein said substance issubstantially punctiform and is rotated about the structure in asubstantially central plane.

10. The apparatus as defined in claim 8, wherein said substance issubstantially planar and is rotated about the structure in said centralarea of the device.

11. The apparatus as defined in claim 10, further compris ing means forshielding said window means from the radiation emanating from saidsubstances, said shield means being associated with said rotating means,and having an opening substantially opposite the location where saidsubstance is secured to said rotating means.

12. The apparatus as defined in claim 8, wherein said rotating meansincludes a driven pulley rotatably mounted outside said device, andmeans attached to said pulley for carrying said substance for rotationin a substantially central plane.

13. The apparatus as defined in claim 12, wherein said carrying means isin the form of a rod which is substantially parallel to the structureand has said substance at its free end remote from said pulley.

14. The apparatus as defined in claim 12, wherein said carrying means isin the form of an arcuate member which partly surrounds the structure,has said substance substantially at its center, and constitutes a shieldfor said radiation emanating from the substance.

15. A method for continuously checking the diameter of elongatedstructures without contact and in a destruction-free manner, comprisingthe steps of moving an elongated structure in substantially axialdirection through an ionization chamber device having a central area andan outer area constituting an ionization chamber; disposing aradioactive substance, in outwardly spaced-apart relation to saidcentral area, so as to provide radioactive radiation within said device;allowing the radiation to impinge on the structure while it passesthrough said central area; making the radiation, which has not beenabsorbed by the structure, act upon electrode means disposed within saidouter area in outwardly spaced-apart relation to the structure and saidsubstance; and measuring an ionization current generated by saidelectrode means, said current being representative of the diameter ofthe structure, on account of the shadow effect of the latter, as it ismoved through said device.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 609,368 Dated September 97 Inventor(s) Jfirgen t a1 It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 5, line 27, and column 6, line 12 "substances", each occurrence,should read substance Column 5, line :5, before "radiation" insert theSigned and sealed this 10th day of October 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOT'ISCHALK Attesting OfficerCommissionerof Patents DRM pomso USCOMM-DC 60376-F'69 U 5 GOVERNMENTPRINTING OFFICE ISIS 0-366-334.

1. An apparatus for checking the diameter of elongated structures, suchas cables and insulated conductors, comprising, in combination, anionization chamber device having a central area and an outer areaconstituting an ionization chamber, means allowing the movement of anelongated structure through said device in substantially central, axialdirection, a radioactive substance disposed in outwardly spaced-apartrelation to said central area, and electrode means disposed within saidouter area in outwardly spaced-apart relation to the structure and saidsubstance, for sensing the radiation which is not absorbed by thestructure, owing to its shadow effect, said electrode means beingadapted to generate an ionization current which is representative of thediameter of the structure as it is moved through said device.
 2. Theapparatus as defined in claim 1, wherein said outer area of the deviceis annular and said electrode means has an axis of symmetry whichcoincides with that of the structure.
 3. The apparatus as defined inclaim 1, wherein said radioactive substances is disposed closer to thestructure than is said electrode means.
 4. The apparatus as defined inclaim 1, further comprising an ionizable medium in said outer area ofthe device, for lodging therein said electrode means.
 5. The apparatusas defined in claim 4, wherein said outer area of the device is sealedfrom said central area, which latter accommodates said means allowingthe movement of the structure as well as said substance.
 6. Theapparatus as defined in claim 5 further comprising window means betweensaid central and said outer areas of the device, said window meanslimiting said central area in radial direction and allowing theradiation to pass therethrough in its way toward said electrode means.7. The apparatus as defined in claim 6, wherein said radioactivesubstance is in annular form and surrounds the structure at asubstantially central, stationary location in the proximity of saidwindow means, tHereby allowing integration of the entire cross-sectionalarea of the structure by radiation, perpendicular to the longitudinalaxis of the structure.
 8. The apparatus as defined in claim 6, furthercomprising means for rotating said radioactive substance concentricallyabout the structure, in the proximity of said window means.
 9. Theapparatus as defined in claim 8, wherein said substance is substantiallypunctiform and is rotated about the structure in a substantially centralplane.
 10. The apparatus as defined in claim 8, wherein said substanceis substantially planar and is rotated about the structure in saidcentral area of the device.
 11. The apparatus as defined in claim 10,further comprising means for shielding said window means from theradiation emanating from said substances, said shield means beingassociated with said rotating means, and having an opening substantiallyopposite the location where said substance is secured to said rotatingmeans.
 12. The apparatus as defined in claim 8, wherein said rotatingmeans includes a driven pulley rotatably mounted outside said device,and means attached to said pulley for carrying said substance forrotation in a substantially central plane.
 13. The apparatus as definedin claim 12, wherein said carrying means is in the form of a rod whichis substantially parallel to the structure and has said substance at itsfree end remote from said pulley.
 14. The apparatus as defined in claim12, wherein said carrying means is in the form of an arcuate memberwhich partly surrounds the structure, has said substance substantiallyat its center, and constitutes a shield for said radiation emanatingfrom the substance.
 15. A method for continuously checking the diameterof elongated structures without contact and in a destruction-freemanner, comprising the steps of moving an elongated structure insubstantially axial direction through an ionization chamber devicehaving a central area and an outer area constituting an ionizationchamber; disposing a radioactive substance, in outwardly spaced-apartrelation to said central area, so as to provide radioactive radiationwithin said device; allowing the radiation to impinge on the structurewhile it passes through said central area; making the radiation, whichhas not been absorbed by the structure, act upon electrode meansdisposed within said outer area in outwardly spaced-apart relation tothe structure and said substance; and measuring an ionization currentgenerated by said electrode means, said current being representative ofthe diameter of the structure, on account of the shadow effect of thelatter, as it is moved through said device.